Johnson Controls GVB Series User Manual

Johnson Controls
Start-Up & Operation Guide | 5586996-JSG-A-0120
59
Operation
Indoor CO
2
When DCV is enabled and the indoor CO
2
level is
greater than the DCV setpoint, the DCV position in-
creases as follows:
• When the CO
2
level is greater than the DCV set-
point + 100 ppm, the DCV position increases 1%
per minute up to a maximum value of 50%
• When the CO
2
level is greater than the DCV set-
point + 200 ppm, the DCV position increases 2%
per minute up to a maximum value of 50%
When DCV is enabled and the indoor CO
2
level is less
than the DCV setpoint, the DCV position decreases as
follows:
• When the CO
2
level is less than the DCV setpoint
– 100 ppm, the DCV position decreases 1% per
minute down to the economizer minimum position
setpoint
• When the CO
2
level is less than the DCV setpoint
– 200 ppm, the DCV position decreases 2% per
minute down to the economizer minimum position
setpoint
When the CO
2
level drops to a value below the DCV
setpoint, the DCV position decreases at the same
rates as above.
Comparative CO
2
When differential DCV is enabled and the outside air
quality (OAQ) is equal to/greater than the IAQ by more
than the DCV differential setpoint, the outside air damp-
er is driven closed regardless of economizer suitability.
DCV and Minimum Outside Airow Control
When both differential DCV and minimum outside airflow
control are enabled at the same time, the unit controller:
• Resets the outside air damper minimum position
setpoint based on an internal algorithm
• When the IAQ sensor PPM is greater than the
IAQ setpoint, the outside airow setpoint is reset
upwards to 5,000 CFM as the IAQ increases from
the IAQ setpoint to the IAQ setpoint + 100 ppm
(Figure 23)
(5,000 CFM) Fixed
Calculated
Outside Airflow
Setpoint
Outside Airflow
Setpoint
IAQ Setpoint
IAQ Setpoint + 100 ppm
Effective IAQ
LD28013
Figure 23: Effective Indoor Air Quality
Continuous Ventilation
This sequence allows the supply fan to run continuous-
ly during the occupied time periods with no demand for
heating or cooling. Continuous ventilation is applicable
to both MZVAV and SZVAV operation.
The fan speed is controlled as follows:
• MZVAV: Supply fan VFD controlled to the active
duct static setpoint
• SZVAV: Supply fan VFD controlled to the SZVAV
minimum fan speed
Continuous ventilation is user enabled/user disabled in
the Views > Details > Supply Fan > Setup menu
Pre-Occupancy Purge
This sequence is only applicable if using the unit con-
roller’s internal schedule
Pre-occupancy purge can be initiated when all of the
below conditions are met:
• The unit must be in an UNOCC mode
• The MAT value must be valid
• The outside air damper is not controlled by a high-
er priority sequence
Pre-occupancy purge is initiated when the time until OCC
mode begins equals the pre-occupancy purge time.
Pre-Occupancy Purge Sequence
• The supply fan VFD is turned ON and controlled
by either MZVAV or SZVAV fan sequences.
• The outside air damper starts to drive open.
• The unit controller turns ON the MZVAV heat com-
mand.

Johnson Controls GVB Series Specifications

General

Brand	Johnson Controls
Model	GVB Series
Category	Air Conditioner
Language	English